Back in April when NPR looked at Republican presidential candidate Mitt Romney's potential running-mate picks, Florida Sen. Marco Rubio and GOP Govs. Mitch Daniels of Indiana and Bob McDonnell of Virginia were on our short list.

But this week, the contours of the GOP veepstakes have shifted. Daniels is reportedly in line to become president of Purdue University. And McDonnell's prospects dimmed after his recent high-profile in-state battles over contraception and mandated pre-abortion ultrasounds.

And what of rising star Rubio, 41, the son of Cuban immigrants and a favorite of Tea Party conservatives?

News accounts this week based on unnamed sources asserted that the former member of the Florida House of Representatives wasn't even being vetted for the job. Romney's initial response when asked about the reports was: "Only Beth Myers and I know who is being vetted." Myers is a longtime Romney aide who is heading the search.

But by late Tuesday, after hours of headlines about Rubio's reported lack of vetting, Romney attempted to bat down the anonymous reports as false. "Marco Rubio is being thoroughly vetted as part of our process," he said.

With all of that in mind, we decided to take another look at the potential GOP veep list, including the recent rise in the stock of former Minnesota Gov. Tim Pawlenty. He is perhaps best remembered nationally as the unlucky candidate who appeared poised to be the Republican vice presidential pick in 2008 before nominee John McCain went rogue with then-Alaska Gov. Sarah Palin.

There are still vice presidential long — and longer — shots out there, including Sen. John Thune of South Dakota and Govs. Brian Sandoval of Nevada and Bobby Jindal of Louisiana. In the wake of conflicting (and embarrassing) reports that Rubio either is or isn't being vetted, we'll leave the party's most prominent Hispanic in the long-shot category for now.

Here's a look at shortlist contenders:

Rob Portman, 56

Current job: U.S. senator from Ohio

Past posts: Director of Management and Budget, and U.S. Trade Representative under President George W. Bush; U.S. representative from Ohio; director of Office of Legislative Affairs and associate counsel to President George H.W. Bush

Upside: Expert on Congress, trade and money issues; from a key swing state; seen as a safe choice

Downside: Strong ties to Bush administration and its policies; polls suggest he doesn't rouse voters in Ohio, and Gallup survey says 62 percent of Americans have never heard of him

Tim Pawlenty, 51

Current job: Romney campaign co-chair; paid speaker represented by Leading Authorities agency (typical fee about $24,000, according to a 2011 FEC filing); serves on several corporate boards

Past posts: Governor of Minnesota; member and majority leader of Minnesota House of Representatives; vice president of software company Wizmo Inc.; Eagan City Council member; lawyer

Downside: Referred to Romney health care overhaul in Massachusetts as the blueprint for "Obamneycare"; taint of failure after missing the vice presidential nod in 2008 and his short-lived, lackluster 2012 presidential campaign

Paul Ryan, 42

Current job: U.S. representative from Wisconsin and chairman of the House Budget Committee